Here is a great article I found that explains in detail how certain plastics degrade and affect objects around them (i.e. the celluloid "rot")

Care of Plastics--WN January 2002

After reading through this, I am left with the conclusion that PVC, while not the best material for straight razor scales, should pose no harm to steel, as it does not emit an acidic gas as it deteriorates.

I hold the position that PVC is a decent enough, economy material for straight razor scales, if the expectation is not that they will last a lifetime.

Someone, please give that a readthrough, and let me know if you are left with the same conclusion I am, or if I am missing something.

Thanks!